UMTS (Universal Mobile Telecommunications System) is the 3rd generation mobile communication system of the wireless technology using WCDMA. In the system architecture of the UMTS terrestrial radio access network (UTRAN) shown in FIG. 1, a radio network controller (RNC) is connected to a core network via an lu interface, the RNCs are interconnected via an lur interface, and one RNC is connected to one or more Node Bs via an lub interface. A Node B contains one or more cells, the cell being a basic unit to which a user equipment (UE) has wireless access (not shown), wherein a radio interface between the UE and the UTRAN is a Uu interface (not shown).
In the protocol documents of the standardization organization 3GPP (the 3rd Generation Partnership Project) of the UMTS, there mainly are TS25.2XX, TS25.3XX and other serial specifications relevant to the UMTS radio interface protocol. In the UMTS radio interface protocol architecture as shown in FIG. 2, the bottom layer is a physical (PHY) layer, and in a control plane, above the physical layer are a media access control (MAC) layer, a radio link control (RLC) layer and a radio resource control (RRC) layer, respectively; in a user plane, the radio interface protocol consists of the physical layer, the MAC layer, the RLC layer and a packet data convergence protocol (PDCP) layer, wherein the PDCP layer is only for a packet-switch (PS) domain. Physical channels are provided by the physical layer, logical channels are provided between the MAC layer and the RLC layer, and transmission channels are provided between the MAC layer and the physical layer.
Uplink transmission channels comprise RACH (Random Access Channel), CPCH (Common Packet Channel), DCH (Dedicated Channel) and the like, and downlink transmission channels comprise BCH (Broadcast Channel), PCH (Paging Channel), FACH (Forward Access Channel), DSCH (Downlink Shared Channel), DCH and the like, wherein the uplink and downlink transmission channels for carrying user data comprise RACH/FACH, CPCH/FACH, DCH/DCH and DCH/(DCH+DSCH). Uplink physical channels comprise PRACH (Physical Random Access Channel), PCPCH (Physical Common Packet Channel), uplink DPCCH (Dedicated Physical Control Channel), uplink DPDCH (Dedicated Physical Data Channel) and the like, downlink physical channels comprise P-CCPCH (Primary Common Control Physical Channel), S-CCPCH (Secondary Common Control Physical Channel), PDSCH (Physical Downlink Shared Channel), downlink DPCCH, downlink DPDCH and the like, and these physical channels have the corresponding relationships, as shown in FIG. 3, with the transmission channels, wherein the DPCH (Dedicated Physical Channel) is a general term of DPCCH/DPDCH. Furthermore, in the downlink, are SCH (Synchronization Channel), CPICH (Common Pilot Channel), AICH (Acquisition Indicator Channel), PICH (Paging Indication Channel), CSICH (CPCH Status Indication Channel), CD/CA-ICH (Collision Detection/Channel Assignment Indication Channel) and the like, all of which are peculiar to the physical layer.
UMTS bearer services mainly comprise conversational and streaming traffic with higher realtime requirements and non-realtime interactive and background traffic. Among RACH, CPCH, FACH, DCH and DSCH for bearing user data, the RACH/FACH is mainly used for non-realtime burst services with a lower rate, and the CPCH and RACH are similar but can provide a higher uplink transmission rate. The DSCH is a transmission channel of a downlink shared type and is greatly adapted to non-realtime burst services with a higher rate, but the DSCH must be used together with a DCH. The DCH is a bidirectional dedicated transmission channel, and upon being established, the resources thereof will be entirely occupied until the channel is released, so the DCH can meet the transmission needs of realtime services. However, when a DCH is used for the transmission of non-realtime services, the utilization ratio of channel bandwidth is lower, so it is necessary to adopt appropriate scheduling and allocation algorithms to improve the utilization ratio of radio resources as much as possible. According to the specification TS34.108 of the 3GPP, the maximum uplink and downlink rates of radio access bearers (RABs) which typically transmit interactive/background services using a DCH (the corresponding physical channel is DPCH) are as shown in FIG. 4, and the current UMTS business systems generally support part or all of these RABs. It can be seen that, due to the uplink/downlink asymmetry of non-realtime packet data services, the typical configuration of uplink and downlink rates is that the uplink rate is less than the downlink rate, and this case still occurs upon a higher rate.
In the current UMTS commercial system based on the R99 version, most of the UE commercial products cannot well support CPCH and DSCH. Thus, other than non-realtime services with a small amount of data that are transmitted using a RACH/FACH, common non-realtime services all need to be transmitted using DCHs. On the other hand, with the expectation of high-rate data services by the practical 3G market, the requirements for 384 kbps bandwidth at most are raised. However, the resources of high-rate channels for non-realtime data services are limited, especially in the downlink direction. On one hand, parts of DCH resources need to be used for adaptive multi-rate (AMR) voice and other realtime services, and on the other hand, due to the uplink/downlink asymmetry of non-realtime services and the limitation on power and orthogonal variable spreading factor (OVSF) channel codes, the resources of the high-rate DCH channels that can be actually used for non-realtime services are made limited. Therefore, an effective method for channel bandwidth resource allocation and rate control is capable of improving radio resource usage and providing users, to the maximum extent, with a data service bandwidth as high as possible, and it is one of the key factors that influences the success of the 3G market in terms of data services.
An important factor in dedicated channel resource allocation and rate control is the actual data rate of a service source. Since the UTRAN only provides radio access bearers and cannot directly obtain service status information of a service source, it is necessary for the UTRAN to judge data rate transmission requirements of the service source by certain measurements. At present, the UMTS mainly adopts a measurement of traffic of a transmission channel to reflect rate requirements of a service source. Details relating to the measurement can be consulted by referring to 3GPP TS25.321, TS25.331 and other specifications, as well as U.S. Patent Application “US 2002/0114280 A1, Method of measuring traffic volume in mobile communication system”. The UTRAN can directly obtain a measurement result of traffic of a downlink MAC and measure control information via RRC, and can also obtain a measurement result of the traffic of an uplink MAC which is provided by a UE. The typical measurement result of the traffic comprises a current amount of buffer occupancies, an average amount of buffer occupancies and a variance of buffer occupancies (in byte), wherein the average amount of buffer occupancies reflects a data rate status of a service carried on the transmission channel, and the variance of buffer occupancies reflects the magnitude of the service bursts carried on the transmission channel.
Besides the traffic, another possible measurement object which reflects a service rate is flow or a channel utilization ratio of each transmission channel. The transmission channel flow is a user data amount of transport blocks transmitted (downlink) or received (uplink) during each TTI (transmission time interval) by each transmission channel, and the transmission channel utilization ratio is defined as follows:
                              transport          ⁢                                          ⁢          channel          ⁢                                          ⁢          utilization          ⁢                                          ⁢          ratio                =                              transport            ⁢                                                  ⁢            channel            ⁢                                                  ⁢            average            ⁢                                                  ⁢                          flow              /              transport                        ⁢                                                  ⁢            channel            ⁢                                                  ⁢            TTI                                transport            ⁢                                                  ⁢            channel            ⁢                                                  ⁢            maximum            ⁢                                                  ⁢            channel            ⁢                                                  ⁢            rate                                              (        1        )            
The flow or channel utilization ratio can be measured more simply than the traffic and can be directly measured in a RNC without needing a measurement report from the UE. In the same way, the mean value and variance of the flow or channel utilization ratio can also be obtained.
A document TR25.922 of the 3GPP recites a handover between a DCH/DCH and a RACH/FACH based on a traffic measurement of a transmission channel, and a method for DCH/DCH rate change. According to the document, when the traffic exceeds a certain threshold, there is a capability for a handover from a RACH/FACH to a DCH/DCH, or improving the DCH rate by decreasing spreading factors. On the contrary, when the traffic is less than a certain threshold, there is a capability for a handover from the DCH/DCH to the RACH/FACH, or improving the DCH rate by increasing spreading factors. In addition, U.S patent application “US 2003/0012217 A1 Channel-type switching to a common channel based on common channel load” , a PCT patent “WO 01/31950 A1, Channel-type switching from a common channel to a dedicated channel based on common channel load”, “WO 01/76304 A1, Channel-type switching based on cell load”, “WO 02/39775 A1, Channel switching in UMTS” and other documents propose as well a plurality of determining methods for a handover between the DCH/DCH and the RACH/FACH.
According to documents TR25.922 and TS25.331 of the 3GPP, during the handover between a DCH/DCH and a RACH/FACH, it is typical to carry out the channel handover based on whether a current configuration of a common channel of a cell is the same as the lately reserved configuration in the UE via RRC processes “Physical Channel Reconfiguration” or “Transmission channel Reconfiguration”; during the DCH/DCH rate change, it is typical to change a channel rate by the RRC process “Physical Channel Reconfiguration”.
In the prior art, what is more concerned is methods for a handover between a DCH/DCH and a RACH/FACH. With regard to bandwidth resource allocation and rate control of a DCH, it is only allowable to determine whether to perform a DCH rate change based on a traffic measurement of a transmission channel. As above-described, bandwidth resources of a DCH, especially the bandwidth resources of the downlink DCH are limited, but the main data transmission is carried out by the DCH. Thus, how to effectively allocate and schedule total available DCH bandwidth resources within a cell is the key to improve the usage of radio resources and provide users with a data service bandwidth as high as possible to the maximum extent. In view of this, the present invention sets forth an effective method for resource allocation and rate control of a dedicated channel.